whole size of the antenna is 30 mm ϫ 27.4 mm. The distance between the horizontal arm of the -shaped slot and the bottom of the ground plane is H 2 . The arms of the -shaped slot have the same width W 2 , the distance of two vertical arms is D, the length of the vertical arm and the horizontal arm are H 1 and L 3 , respectively. RESULTS AND DISCUSSIONParameters L 1 , W 1 , G, N are firstly optimized using the Ansoft High Frequency Structure Simulator (HFSS) to ensure good VSWR performance through the whole UWB band. Finally, they are chosen to be L 1 ϭ 15 mm, W 1 ϭ 24 mm, G ϭ 0.45 mm, N ϭ 5, whereas the width and the axial ratio of the half ellipse-shaped ground are fixed to 30 mm and 0.8, respectively.The parameters such as H 1 , D, and L 3 of the -shaped slot are studied to see the influences on the performances of the antenna while W 2 ϭ 0.5 mm. Figure 2 shows the simulated VSWR for different values of these parameters which are listed in Table 1. It is clearly seen that the center frequency of the notched band can be varied from 5.2 to 5.8 GHz by properly selecting the parameter values. For the purpose of comparison, as is shown in Figure 3, a prototype of the proposed antenna with H 1 ϭ 6.5 mm, D ϭ 5 mm, L 3 ϭ 9 mm, W 3 ϭ 2.2 mm, W 4 ϭ 0.3 mm was fabricated and tested. The measurement was made with a Wiltron 37269A vector network analyzer. As can be seen from the measured results, the proposed antenna provides a sufficiently wide impedance bandwidth (VSWR Ͻ 2) of 7.9 GHz (3.1-11 GHZ), and has a frequency notch of about 600 MHz (5.4 -6.0 GHZ) for band rejection of the WLAN frequency band. It is also seen that without the -shaped slot, the antenna can operate from 3.1 to 10.7 GHz which covers the whole UWB band. It is clear seen that the measured results agree well with those from the simulation. The measured radiation patterns at 4 GHz and 7 GHz are presented in Figure 4. It can be seen that the patterns of the proposed antenna at frequencies out of the notched band present omnidirectional and stable radiation characteristic in the xy-plane (H-plane) over the operating frequency range, which are similar to that of the typical monopole antenna. Because of the symmetry in structure, symmetrical radiation patterns are seen in the xy and yz planes, as depicted in the plots. The simulated peak gain is plotted in Figure 5, the result presents that the antenna is successfully performed with the rejection in the 5-6 GHz WLAN band. CONCLUSIONA compact CPW-fed planar monopole UWB antenna with bandnotched characteristic at around 5.8 GHz has been proposed and implemented. The total antenna size is 30 mm ϫ 27.4 mm ϫ 1 mm. By embedding a -shaped slot, the band-notched characteristic can be obtained. The center frequency of the notched band can be varied from 5.2 to 5.8 GHz by properly selecting the parameter values. It is seen from the measured results that the proposed antenna has omnidirectional radiation patterns. Therefore, the proposed antenna is suitable for the UWB communication applications and prevents interfere...

An efficient sub-entire-domain (SED) basis function method has been proposed to analyze large-scale periodic structures with finite sizes accurately. The SED basis function is defined on the support of each single cell of the periodic structure. After introducing dummy cells with respect to an observation cell, the real physics of SED basis function is captured accurately by solving a small-size problem. Further analysis has shown that all kinds of SED basis functions used in the periodic structure can be obtained by solving a single small problem. Hence, the original large-scale problem involving = 0 unknowns is decomposed into two small-size problems, one of which contains 9 unknowns and the other of which contains only 0 unknowns. Here, 0 is the total cell number in the periodic structure and is the number of subdomain basis functions in each unit cell. Several examples are given to test the validity and efficiency of the proposed method. Numerical results from the new method have excellent agreements with those from the conventional method of moments. However, the CPU time has been greatly reduced. Index Terms-Electromagnetic bandgap materials, frequency selective surface, metamaterials, method of moments (MoM), periodic structures, sub-entire-domain (SED) basis function.

A quantitative study is presented for the low frequency breakdown of the electric‐field integral equation (EFIE) with the Rao–Wilton–Glisson basis function. The low frequency limit is ascertained hereby. Numerical experiments validate the conclusion. The line testing method is also compared with the Galerkin testing to dispel the misconception in the literature. The study thus provides a guideline for the application of EFIE in the full‐field regime. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1159–1162, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23324

Lubricants are of key importance for mechanical processing, and exist in nearly every mechanical system. When the equipment is in operation, debris particles will be generated in mechanical lubricants. The detection of debris particles can indicate the wear degree of machinery components, and provide prognosis warning for the system before the fault occurs. In this work, a novel type of inductive debris sensor consisting of two excitation coils and two sensing coils is proposed for online debris monitoring. The developed sensor was proven to be of high sensitivity through experimental verification. The testing results show that, using the designed sensor, ferrous metal debris with a size of 115 μm and nonferrous metal debris with a size of 313 μm in a pipe with an inner diameter of 12.7 mm can be effectively detected. Moreover, the proposed inductive debris sensor structure has better sensitivity at higher throughput and its design provides a useful insight into the development of high-quality sensors with superior performances.

We present a fast method for solving low‐frequency complex problems over a frequency band. In this method, we apply fast multipole method to accelerate the solution process of augmented electric field integral equation with perturbation method (enhanced A‐EFIE). As the current is expanded as a power series in frequency in enhanced A‐EFIE, results over a frequency band can be obtained by one low‐cost simulation. Real circuit problem with one million unknowns is used to demonstrate the effectiveness of the method. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2153–2158, 2014